Function of the Week
scale_fill_gradient()In this document, I will introduce the scale_fill_gradient function and show what it’s for.
The scale_fill_gradient function() allows you to manually assign the colors used to map a continuous variable to a color gradient in a plot.
Required Arguments:
low = “” (color of the lowest value of your gradient)
high = “” (color of the highest value of your gradient)
diamonds %>% ggplot() +
aes(x = carat,
y = price,
fill = carat) +
geom_point(shape = 21, size = 2) +
scale_fill_gradient(low = "blue",
high = "red") +
labs(title = "Diamond Price vs Carat Plot",
x = "Carat",
y = "Price",
fill = "Carat") +
theme_minimal()
sfg_plot <- diamonds %>% ggplot() +
aes(x = x,
y = y,
fill = z) +
geom_point(shape = 21) +
scale_x_continuous(limits = c(3, 9.5)) +
scale_y_continuous(limits = c(3,10)) +
scale_fill_gradient(name = "Z (mm)", low = "yellow", high = "red", limits = c(2,6)) +
labs(title = "Diamond Dimensions X, Y, and Z in mm",
x= "X (mm)",
y = "Y (mm)") +
theme_minimal()
default_plot <- diamonds %>% ggplot() +
aes(x = x,
y = y,
fill = z) +
geom_point(shape = 21) +
scale_x_continuous(limits = c(3, 9.5)) +
scale_y_continuous(limits = c(3,10)) +
scale_fill_continuous(name = "Z (mm)", limits = c(2,6)) +
labs(title = "Diamond Dimensions X, Y, and Z in mm",
x= "X (mm)",
y = "Y (mm)") +
theme_minimal()
grid.arrange(default_plot, sfg_plot, nrow = 2)Warning: Removed 22 rows containing missing values or values outside the scale range
(`geom_point()`).
Removed 22 rows containing missing values or values outside the scale range
(`geom_point()`).
na.value = can be used to assign a fill color to any na.values in the scale
# Create a plot with geom_tile to visualize ozone levels
airquality %>% ggplot() +
aes(x = factor(Month),
y = Day,
fill = Ozone) +
geom_tile() +
scale_fill_gradient(low = "blue", high = "red", na.value = "light grey") +
labs(title = "Ozone Concentration by Date",
x = "Month",
y = "Day",
fill = "Ozone") +
theme_minimal()
scale_fill_gradient() has tons of other accepts arguments including…
name = , space = “” , transform = , guide = , aesthetics =
Related Functions:
scale_fill_gradient2() allows you to assign a midpoint value and color to your scale.
midpoint = assigns midpoint value
mid = assigns midpoint color.
# Create a tile plot by date filling with temperature where the lows are blue, the highs are red, and the days closer to the mean temp get closer to white.
airquality %>% ggplot() +
aes(x = Month,
y = Day,
fill = Temp) +
geom_tile() +
scale_fill_gradient2(low = "blue",
high = "red",
midpoint = mean(airquality$Temp),
mid = "white") +
theme_minimal()
scale_fill_gradientn allows you to assign more than 3 values to your scale using colors=
values = accepts values between 0 and 1 and is used to assign the relative positions along the gradient that you want each color to be mapped to.
This is useful if you have a few very high or very low values and you don’t want to remove them, but also don’t want to shift all the colors of your gradient according to a few values.
diamonds2 <- diamonds %>%
mutate(long_dim = pmax(x,y,z))
diamonds2 %>% ggplot() +
aes(x = carat,
y = long_dim,
fill = price) +
geom_point(shape = 23, size = 1) +
scale_y_continuous(limits = c(3,10)) +
scale_x_continuous(limits = c(0,4)) +
scale_fill_gradientn(
colors= c("red", "orange", "yellow", "green", "blue", "purple"),
values = c(1, 0.8, 0.6, 0.4, 0.2, 0)) +
labs(title = "Longest Dimension vs Carat Filled by Price",
x = "Carat",
y = "Longest Dimension (mm)",
fill = "Price") +
theme_minimal()Warning: Removed 16 rows containing missing values or values outside the scale range
(`geom_point()`).
It is a useful tool for customizing your plots. Ggplot’s default gradients are not very aesthetic, so scale_fill_gradient() is great. scale_fill_gradient2 and scale_fill_gradientn give you even more freedom when it comes to customization.